Summary On 04 November 2003, the deHavillandDHC-8-102 aircraft (registrationC-GONJ, serial number095), operating as Air Canada Jazz Flight8946, was on a scheduled flight from Ottawa/Macdonald-Cartier International Airport, Ontario, to Montral International Airport (Dorval), Quebec, with 19passengers and a crew of three. The aircraft left the gate and proceeded to the de-icing pad where it was de-iced to remove ice that had accumulated during the previous flight and freezing rain that had accumulated while the aircraft was on the ground at Ottawa. The aircraft then taxied to Runway07 and was cleared for take-off. The crew carried out normal pre-take-off checks and at 1412 eastern standard time commenced the take-off run. On rotation, the pilot felt a restriction to movement of the pitch controls and, as a result, the pilot rejected the take-off. After clearing the runway, the crew moved the elevator controls through their full range of movement and found them free of restriction. The aircraft returned to the gate where maintenance inspected the aircraft and found the controls operating properly and free of restriction. Some freezing rain drops and residual de-icing fluid were found on the horizontal stabilizer and the elevator surfaces, but there were no large pieces of ice. The aircraft was de-iced again and proceeded to Montral. Ce rapport est galement disponible en franais. Other Factual Information The aircraft and flight crew had been in Ottawa overnight and had flown a round-trip to the Toronto City Centre Airport, Ontario, earlier on the day of the occurrence. The return flight landed at Ottawa at approximately 1053 eastern standard time.1 Freezing rain was encountered below 5000feet on the approach and some ice accumulated. The aircraft was on the ground, parked outside, for approximately 2hours 30minutes prior to leaving the gate on the next flight, during which time there was precipitation in the form of light and moderate ice pellets, light freezing rain, and light rain. Prior to boarding Flight8946, the crew inspected the aircraft and observed ice on the critical surfaces, the nose, and the propellers and icicles on the trailing edges of the wings and horizontal tail. Light ice pellets and light freezing rain were falling at that time. Before engine start, the propellers were de-iced with TypeI freezing point depressant (FPD) fluid. The engines were started at 1318 and the aircraft taxied from the gate at 1320, arriving at the de-icing ramp at 1324. There was a delay of approximately 30minutes before de-icing started due to an aircraft ahead and a shift change at the de-icing facility. De-icing using TypeI fluid was carried out between 1353 and 1408. The aircraft was parked on a heading of 140 degrees magnetic. During the de-icing, there was a crosswind from the aircraft's left; 070 at 15 knots with gusts to 20 knots. Two trucks were used, initially positioned on either side of the fuselage behind the wings and in front of the tail. The truck on the left side de-iced the left wing while the truck on the right de-iced the right wing. The truck on the left moved to the nose of the aircraft to remove the ice from the previous flight while the truck on the right remained behind the starboard wing and de-iced both sides of the horizontal stabilizer and elevators. On completion of de-icing, de-icing personnel saw no ice on any aircraft surfaces. The crew was aware that a resumption of freezing precipitation before take-off would necessitate returning for further de-icing; however, no precipitation fell during de-icing or while taxiing for take-off. When de-icing was complete, the de-ice lead advised the flight crew. They left the de-icing pad at approximately 1408 and proceeded to Runway07 for take-off. The crew carried out normal pre-take-off checks, including a check of the controls, performed by the pilot not flying (PNF). The take-off run began at 1412. When attempting to rotate, the pilot flying (PF) felt a restriction to aft movement of the control yoke and rejected the take-off. After clearing the runway, a control check was carried out but there was no restriction. The aircraft returned to the ramp. There was a delay of 30minutes before the aircraft received a gate assignment and was shut down. By that time, freezing rain was again falling. A maintenance technician verified that the elevator controls were free of restriction and moving correctly, then inspected the top surface of the horizontal stabilizer. The technician found freezing rain drops and residual de-icing fluid, but no large pieces of ice. The aircraft, released by maintenance and de-iced, proceeded to Montral, Quebec. Ottawa airport weather reports indicated that precipitation, in the form of light ice pellets, rain, and freezing rain, fell during the period that the aircraft was on the ground between flights. There was no precipitation between 1339 and 1453, then light freezing rain resumed. The weather recorded at the time of the rejected take-off was as follows: wind 070T at 15knots with gusts to 20knots; temperature -2and no precipitation. De-icing was carried out by Air Canada using two Global model2110TE-EC-AP trucks equipped with a telescopic boom and articulating enclosed cab with a reach and height of 28feet. Each truck was operated by a driver and a boom operator, and the overall operation was controlled by a de-icing lead. The lead had communication with the flight crew and with the truck drivers, and the truck drivers had communication with their respective boom operators. Manning, qualifications, training, and procedures were in accordance with the Air Canada Jazz Ground Icing Program manual2 and with the company operations manual (COM)3. A total of 503litres of TypeI fluid was used for the wings, tail, and nose, which reportedly is more than average but not inconsistent with the aircraft's exposure to freezing precipitation. Both pilots held airline transport pilot licences and were appropriately qualified for this flight. They had received surface contamination training in accordance with company requirements, and both had adequate rest the previous night. There were no fatigue or duty-time related issues. According to records, the aircraft was maintained in accordance with current regulations. There were no outstanding maintenance issues or indication of pre-existing mechanical failure or other condition that would have contributed to this incident. The aircraft was equipped with a cockpit voice recorder (CVR) and a flight data recorder (FDR) as required by Canadian Aviation Regulations (CARs). The CVR was recorded over during the subsequent flight and was not available for investigation. FDR data are presented at AppendixA. The sample rate for the FDR was one sample per second. The following information was derived from the FDR: During the control check, the FDR recorded the elevators moving from fully trailing edge down to near fully trailing edge up and back to neutral in less than three seconds, during which both elevators moved in unison. Full range of travel is 20trailing edge down to 20trailing up. It is likely that the elevators reached the full range of trailing edge up travel but were not recorded due to the rate of control movement relative to the sample rate of the FDR. The elevators were then held near neutral while the lateral controls were checked, during which a split of approximately 4developed between the two elevators and remained until the elevators were returned to the fully trailing edge down position on completion of the control checks. At the beginning of the take-off run, both elevators moved in unison to approximately 7.5trailing edge down at 45knots indicated airspeed (KIAS). As the aircraft accelerated, a split developed, the left elevator essentially not moving while the right elevator continued to move trailing edge up to a maximum of 2.2up. The maximum split was 8at 107KIAS. After the take-off was rejected, as the aircraft decelerated through 65KIAS (the speed at which the PF normally releases the control yoke to use the tiller), the right elevator went full trailing edge down while the left elevator hung at about 10trailing edge down for 10seconds. At 50KIAS, the elevators both moved abruptly to about 15trailing edge up and back to full trailing edge down, consistent with the PNF locking the controls in accordance with normal rejected take-off procedures. Both elevators moved in unison with no indication of hang-up when the controls were exercised through their range of movement after the aircraft cleared the runway. During the subsequent take-off, when no elevator restriction was encountered, both elevators moved progressively to approximately 1.5trailing edge down at 45KIAS and to 1.5trailing edge up by 65KIAS. They remained at that position until 98KIAS when the pilot initiated rotation for take-off; both elevators moved to over 10trailing edge up. These normal elevator control positions are shown in AppendixA for comparison with the positions during the rejected take-off. Dash 8 pitch control is effected by manually operated, spring-tab assisted elevators. The elevators are attached behind the horizontal stabilizer with a clearance of 0.15to 0.25inches between the leading edge of the control surface and the shroud on the trailing edge of the stabilizer. The left and right elevators are operated by independent mechanical control circuits that are normally interconnected at the control columns. There is a disconnect system to allow either side to operate independently of the other in the event of a malfunction. Control column inputs are transmitted through a series of cables, pulleys, bellcranks, push rods, torque tubes, and torsion springs to the elevator and to the spring tab that provides aerodynamic assistance to elevator movement. There is no cockpit indication of elevator position or of differences between the elevators. The Dash 8 is certified4 in compliance with Federal Aviation Regulation (FAR)25.1419 for flight in icing conditions subject to the aircraft being operated in accordance with the manufacturer's Aircraft Flight Manual (AFM).5 The AFM contains a warning as to conditions that could possibly exceed the capability of the ice protection system and degrade the performance and controllability of the aircraft. The AFM provides guidance as to the recognition of severe icing conditions and a procedure in the event that severe icing is encountered. The wording of the AFM is consistent with that required by a Federal Aviation Administration (FAA) airworthiness directive6 to U.S. operators concerning operation in icing conditions. A service letter7 issued by the aircraft manufacturer reflects the need for the aircraft's critical surfaces to be free of contaminants. It also indicates the possibility that dehydrated anti-icing fluid residue will accumulate in the aerodynamically quiet area between the control surface and the shroud immediately ahead of it. It states that jams could be associated with freezing of rehydrated residue. An operating data manual supplement8 addresses icing precautions and de-icing procedures and provides performance adjustment following the application of de-icing and anti-icing fluids. CAR 602.11, relating to aircraft icing, prohibits take-off with frost, ice, or snow adhering to any critical surface and requires that Part 705 operators establish a program that complies with CAR Standard622.11, Ground Icing Operations, and operate in accordance with that program. Air Canada Jazz complies with the CAR requirement through its ground icing program as presented in the COM and its Ground Icing Program manual. CAR Standard622.11, Section7 states that the operator's program must provide aircraft-specific instructions and procedures to be followed by flight crew and other personnel for detecting contamination on the critical surfaces of aircraft. Two types of inspection that meet regulatory requirements are defined. They are: critical surface inspection - is a pre-flight external inspection of critical surfaces conducted by a qualified person [. . .] to determine if they are contaminated by frost, ice, or snow. Under ground icing conditions, this inspection is mandatory. pre-take-off contamination inspection - is an inspection conducted by a qualified person, immediately prior to take-off, to determine if an aircraft's critical surfaces are contaminated by frost, ice, or snow. This inspection is mandatory under some circumstances [as specified in the operator's program]. CAR Standard622.11, Section7.1.3 provides additional guidance for the pre-take-off contamination inspection, allowing for inspection from the inside or outside of the aircraft, and allowing the use of representative aircraft surfaces to judge the extent of contamination. The inspection may be visual or tactile except that, for aircraft without leading edge devices, it must be tactile unless other procedures have been specifically approved. Where only a visual inspection is done, the operator's program is required to specify the conditions, such as weather, lighting, and visibility of critical surfaces, under which the inspection can be carried out. The approved Air Canada Jazz Ground Icing Program manual and the COM state procedures for de-icing the Dash8. There is a specific instruction to remove snow and ice between the elevator leading edges and all tabs and shrouds. The Ground Icing Program manual states that a critical surface inspection is mandatory under ground icing conditions and that some aircraft require a tactile inspection of critical surfaces. For the Dash8, the Ground Icing Program manual calls for a tactile inspection to check that dry snow has not adhered during layovers and for presence of ice in the engine intake prior to engine start. The COM requires a pre-take-off contamination inspection when minimum hold-over times are exceeded. For the Dash8, the pre-take-off contamination inspection is a visual inspection by the pilot in the left seat of a representative surface, the left wing outboard roll spoiler. This inspection is considered to satisfy the intent of the tactile inspection called for by CAR Standard622.11 for aircraft without leading edge devices. CAR 705.124 requires that operators establish and maintain a training program that includes aircraft surface contamination training that, according to CARs Standard725.124, includes training in in-flight icing recognition and operations in icing conditions. Transport Canada (TC) publications TP14052E9 (Erefers to English language, Fwould indicate French) and TP10643E10 provide additional guidance for ground icing programs and for critical surface contamination training. TP 14052 and TP10643 both state that aircraft are not certified to fly in freezing rain conditions. TP10643 indicates that CARs, the COM, and the AFM are the final authority in the case of conflict. TP14052 states that it replaces all previous Commercial and Business Aviation Advisory Circulars (CBAACs) on the subject and must be included in the company training program. Two CBAACs11 on the subject of airborne icing remain available on the TC Web site. CBAAC0130R acknowledges that aircraft may encounter conditions that are outside the certification envelope and provides procedures for such circumstances, including procedures that may take precedence over operating guidance in aircraft flight manuals. TP 10643 provides no guidance for flight in severe icing beyond stating that aircraft are not certified to fly in freezing rain and it makes no reference to these advisory circulars. In 1996, in a series of 18airworthiness directives (ADs), including AD96-09-25, applicable to transport category aircraft equipped with pneumatic de-icing boots and non-powered roll control systems, the FAA mandated changes to aircraft flight manuals to address flight in severe icing conditions. The preamble to these ADs states that flight outside the icing certification envelope occurs during the normal service life of an airplane; therefore, guidance is necessary for flight crews. FAA Technical ReportDOT/FAA/AR-01/91, A History and Interpretation of Aircraft Icing Definitions and FAA Rules for Operating in Icing Conditions, dated November2001, contains no linkage between operating rules and certification criteria, but states that there is confusion resulting from differences between icing intensity definitions and operating rules for flight in icing conditions. FAA advisory circular (AC)25.1419-112 provides guidance for certification of aircraft for flight in known icing, including guidance as to the contents of the AFM. It specifically cites AD96-09-25 as an appropriate means of providing information on flight in severe icing. In Canada, the certification standard for flight into known icing13 is identical to that of the U.S. Except as provided in CAR602.07, which requires that aircraft be operated in accordance with the limitations in the AFM, no CAR prohibits flight outside envelopes or test limits contained in the certification standard of the aircraft. Certification standards14 do not require that atmospheric icing conditions associated with certification of ice protection equipment be presented in the AFM either as a limitation or otherwise. The Air Canada Jazz COM provides guidance and operating restrictions for flight in icing conditions. Take-off is permitted in freezing precipitation when the ground icing program is complied with. Freezing rain is defined as to be avoided; the operating restriction is not to operate in known severe icing. When moderate or severe icing conditions are forecast, Air Canada Jazz obtains pilot reports and SIGMETs/AIRMETs to verify actual conditions. Dispatch consults the pilot-in-command if there is doubt as to the ability to avoid such conditions. A review of records revealed three previous incidents of interest involving Dash 8 aircraft: one in which elevators jammed in flight due to freezing of wet snow in the gap between the elevators and the horizontal stabilizer;15 one in which elevator spring tab movement restricted in flight, probably due to accumulation of ice or frozen snow in the gap between the spring tab and the elevator;16 and one in which restricted elevator spring tab movement was possibly due to freezing of rehydrated residue of previously applied anti-icing fluids.17 Freezing of rehydrated residue was also implicated in an occurrence involving a BAe146 aircraft, which has a similar elevator control system.18